The present invention relates to an apparatus for driving a semiconductor laser. In particular, the invention concerns an apparatus for controlling output power of a semiconductor laser used as a light source for a digital optical disk device.
Recently, there has been developed a digital optical disc storage system for recording and reproducing information, in which laser light is focussed onto a metallic film deposited on a disc in the form of a minute spot for thermally recording given information on the metallic film by modulating laser light by the given information, while for reproducing the recorded information the metallic film is irradiated with laser light of such a power level at which the metallic film is protected from injuries or damages. As the laser light source for this type of apparatus, a gas laser was heretofore employed. At present, a semiconductor laser has become increasingly popular in place of the gas laser to meet the demand for miniaturization of the device, reduction in power consumption and the like. However, this semiconductor laser suffers a disadvantage in respect that the output characteristic thereof is subjected to changes or variations under the influence of ambient temperature or as time elapses.